In chemical vapor deposition (CVD) processes, including epitaxial growth processes, uniformity in the thickness of a deposited film on a substrate is dependent on, among other factors, uniformity in the flow distribution of gasses within the process chamber. As the requirements for uniformity in film thickness become more stringent, the desire for more uniform flow rate distribution of gasses in the process chamber increases.
In conventional CVD devices, a source gas is introduced into the process chamber through a gas manifold. The gas manifolds of conventional CVD devices do not provide adequate control of the gas flow distribution across the substrate surface in the processing chamber.
For example, baffle plates used in conventional gas manifolds have fixed hole sizes that cannot be adjusted without replacing the entire baffle plate. Thus, conventional baffle plates do not permit selective adjustment of the gas flow distribution across the substrate surface, which may be needed when changing process parameters such as the flow rate of the process gas.
Additionally, injection port liners and inject inserts used in conventional gas manifolds do not provide sufficient uniformity in the gas flow distribution across the substrate surface. For example, some injection port liners may include multiple flow zones having different process gases or gas flow rates which feed into a single channel defined within the inject insert. As a result of the “crosstalk” between the multiple flow zones feeding into a single inject insert channel, attempts to tune the gas flow distribution within the processing chamber by varying the type of gas or gas flow rate in the different flow zones have unpredictable tuning results.
Additionally, in operation, localized zones of cyclically flowing gas, known as “recirculation cells,” often form within the channels of inject inserts used in conventional gas manifolds. Recirculation cells result in degraded uniformity of the gas flow distribution within the processing chamber, which results in strong variations in epitaxially-grown films.
The foregoing problems attributable to conventional gas manifolds are amplified when the flow rate of the process gas is increased, which is desirable to increase the throughput of the CVD device.
Accordingly, a need exists for a gas manifold capable of delivering a more uniform flow rate distribution across the surface of a substrate within the processing chamber.
This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.